The invention relates to a load bearing access cover, assembly or components
thereof, to close an opening, for example an in ground utility chamber or similar.
The access cover has a unitary cast structural support that defines an upper side
and lower side. The structural support has a lattice of structural webs defining
a plurality of interstices; at least some interstices are open to both said upper
and lower sides. The structural support also has a frame portion at least in part
surrounding a periphery of the lattice. The frame portion connects between at
least some of the structural webs. A top plate is engaged, or engageable, to the
structural support from above. The top plate is at least coextensive with the
strucutral support. The strucutrual support and the top plate are engaged or
engageable to form a unitary load bearing structure.

1. A load bearing access cover, assembly or components thereof, to at least in part close an opening, comprising or including, a unitary cast structural support providing member (hereinafter "structural support") defining an upper side and a lower side comprising, a) a lattice of structural webs defining a plurality of interstices, wherein at least some interstices are open to both said upper and lower sides, and b) a frame portion at least in part surrounding a periphery of said lattice, said frame portion connecting between at least some of said structural webs, and a top plate engaged, or engageable, to said structural support providing member from above, said top plate being at least substantially coextensive with said structural support, wherein said structural support and said top plate are engaged or engageable to form a unitary load bearing structure. 2. A load bearing access cover as claimed in claim 1 wherein said structural support is generally of a slender thickness (between said upper and lower sides) planar profile.

3. A load bearing access cover as claimed in claim 2 wherein said top plate locates to the upper side of and parallel to said planar profile of said structural support.

4. A load bearing access cover as claimed in any one of claims 1 to 3 wherein said load bearing access cover is adapted in use to engage a surrounding or perimeter frame.

5. A load bearing access cover as claimed in claim 4 wherein said frame portion engages in use said surrounding or perimeter frame.

6. A load bearing access cover as claimed in any one of claims 1 to 5 wherein said at least some of said interstices are at least in part bounded by an at least in part surrounding flange running between bounding said structural webs.

7. A load bearing access cover as claimed in any one of claims 1 to 6 wherein at least said structural support is at least predominantly of aluminium.

8. A load bearing access cover as claimed in any one of claims 1 to 7 wherein said structural support providing member is cast as a unitary item. 9. A load bearing access cover as claimed in any one of claims 1 to 8 wherein said top plate is aluminium.

10. A load beating access cover as claimed in any one of claims 1 to 9 wherein said top plate includes a major side facing said structural support providing member, and on said major side there are means to locate with at least some of said structural webs.

11. A load bearing access cover as claimed in claim 10 wherein said means to locate are lugs or flanges upstanding from the major surface of said top plate and abut either side of said structural webs of said structural support providing member.

12. A load bearing access cover as claimed in any one of claims 10 or 11 wherein said major side facing said structural support of said top plate may have structural webs complimentary and able to be engaged to at least one or more structural webs in said structural support.

13. A load bearing access cover as claimed in any one of claims 1 to 12 wherein said top plate is engaged to said structural support by any one or more of: a) Welding b) Threaded or similar fastening, c) Adhesives, or d) any combination thereof.

14. A load bearing access cover as claimed in any one of claims 10 to 13 wherein said top plate includes, on its upper presenting major surface, a tread or grip enhancing pattern. 15. A load bearing access cover as claimed in any one of claims 4 to 14 wherein said access cover has locking means to releasably engage with a surrounding or perimeter frame of in-ground access opening.

16. A load bearing access cover as claimed in any one of claims 1 to 15 wherein said frame portion is continuous about the periphery of said lattice of structural webs. 17. A load bearing access cover as claimed in any one of claims 1 to 16 wherein said structural webs include a first plurality of structural webs extending in a first direction and a second plurality of structural webs extending in a second direction, perpendicular to said first plurality, both said first and second pluralities extending between inner edges of said frame portion. 18. A load bearing access cover as claimed in any one of claims 1 to 16 wherein said structural support is ckcular in shape having radial webs.

19. A load beating access cover as claimed in any one of claims 1 to 18 wherein said surrounding flange is disposed more to the lower side of said structural webs.

20. A method of forming a load bearing access cover, assembly or components thereof, said load bearing access cover to at least in part close an opening, comprising or including the steps of, a) providing a unitary cast structural support providing member (hereinafter "structural support") defining an upper side and a lower side including, i) a lattice of structural webs defining a plurality of interstices, wherein at least some interstices are open to both said upper and lower sides, and ϋ) a frame portion at least in part surrounding a periphery of said lattice, said frame portion connecting between at least some of said structural webs, and b) engaging a top plate to said structural support providing member from above, said top plate being at least substantially coextensive with said structural support, to form a unitary load bearing structure. 21. A method as claimed in claim 20 wherein said top plate is engaged to said structural support by any one or more of: a) Welding b) Threaded or similar fastening, c) Adhesive s, or d) any combination thereof.

22. A method as claimed in claim 21 wherein said top plate is engaged to said structural surround by welding.

23. A method as claimed in any claims 20 to 22 wherein said top plate locates to the upper side of and parallel to a planar profile of said structural support. 24. A method as claimed in any one of claims 20 to 23 wherein said at least some of said interstices are at least in part bounded by an at least in part surrounding flange running between bounding said structural webs.

25. A method as claimed in any one of claims 20 to 24 wherein at least said structural support is at least predominantly of aluminium. 26. A method as claimed in any one of claims 20 to 25 wherein said structural support providing member is cast as a unitary item.

27. A method as claimed in any one of claims 20 to 26 wherein said top plate is aluiTiinium.

28. A method as claimed in any one of claims 20 to 27 wherein said top plate includes a major side facing said structural support providing member, and on said major side there are means to locate with at least some of said structural webs.

29. A method as claimed in claim 28 wherein said means to locate are lugs or flanges upstanding from the major surface of said top plate and abut either side of said structural webs of said structural support providing member.

30. A method as claimed in any one of claims 28 or 29 wherein said top plate includes, on its upper presenting major surface, a tread or grip enhancing pattern.

31. A load bearing access cover as claimed in any one of claims 20 to 30 wherein said method includes the step of locating locking means at least in part in said access cover releasably engage with a surrounding or perimeter frame of an in-ground access opening. 32. An in situ opening cover located in or on the ground and engaged with a complementary perimeter frame, said opening cover comprising or including, a unitary cast structural support providing member (hereinafter "structural support") having an upper side and a lower side including, a) a lattice of structural webs defining a plurality of interstices, wherein at least some interstices are open to both said upper and lower sides, and b) a frame portion at least in part surrounding a periphery of said lattice, said frame portion connecting between at least some of said structural webs, and a top plate engaged to the upper side of said structural support providing member, said plate being of a perimeter commensurate with a perimeter of said structural support, wherein said structural support and said top plate are engaged or able to be engaged to form a unitary load bearing structure.

33. A method of making an access cover as herein described with reference to any one or more of the drawings without the use of sand casting. A load bearing access cover as herein described with reference to any one or more of the accompanying drawings.

Description:

"ACCESS COVER"

The present invention relates to an access cover and in particular although not solely relates to an access cover to be provided for use in conjunction with a manhole, utility chamber opening or similar opening normally provided in a ground level surface.

Access covers are also often called manhole covers and are provided to cover or close an opening. Such an opening may for example be an access hole in a road, foot path, tarmac or the like. An access cover is designed to provide a means of closing the opening when access through the opening is not necessary or undesirable. The access cover can be removed from the opening to thereby allow for the opening to provide access there through and into the below ground located regions. Such below ground regions may contain utilities such as for example sewage pipes, storm pipes, telecommunication pipes and connections, underground passage ways, gas connections, electrical conduits and the like. Such utilities are often contained in a below ground utility chamber and the access cover closes the opening to the utility chamber. Access covers may also be provided in the form of grates which provide a restricted degree of closure to an in ground opening.

Where access covers are provided in regions where significant loading is likely to be experienced, the access covers need to have consideration strength to ensure that the cover remains intact and undamaged when loading acts onto it. For example some access covers are provided in road ways, footpaths, runways and taxiways. They therefore need to be of sufficient strength to not failure under high repeat loading of cars, trucks, aircraft and other heavy equipment.

Normally such access covers have been made from cast iron and similar materials to meet such strength requirements and keep manufacturing costs down. One of the major disadvantages of the use of cast iron for access covers is its weight. The weight of access covers made from cast iron make them expensive to transport to the locations for installation, and also, once installed, makes them difficult to manipulate for moving them between an opening, closed and open condition.

An alternative material that is still economic to manufacture and overcomes the weight problem is aluminium. Whilst the use of aluminium does result in a lighter weight access cover, achieving the sufficient strength required can be difficult to achieve consideration. Therefore such aluminium access covers are often limited to low load use, for example footpath and do not appear to have been incorporated in high load carriage way type use.

A further difficulty is struck when moulding complex and hollow shapes in aluminium.

Accordingly it is an object of the present invention to provide an access cover which is simple and economic to produce or which will at least provide the public with a useful choice.

In a first aspect the present invention may be said to broadly consist in a load bearing access cover, assembly or components thereof, to at least in part close an opening comprising or including, a unitary cast structural support providing member (hereinafter "structural support") defining an upper side and a lower side comprising, a) a lattice of structural webs defining a plurality of interstices, wherein at least some interstices are open to both said upper and lower sides, and b) a frame portion at least in part surround a periphery of said lattice, said frame portion connecting between at least some of said structural webs, and a top plate engaged, or engageable, to said structural support providing member from above, said top plate being at least substantially coextensive with said structural support, wherein said structural support and said top plate are engaged or engageable to form a unitary load bearing structure.

Preferably said structural support is generally of a slender thickness (between said upper and lower sides) planar profile.

Preferably said top plate locates to the upper side of and parallel to said planar profile of said structural support. Preferably said load bearing access cover is adapted in use to engage a surrounding or perimeter frame.

Preferably said frame portion engages in use said surrounding or perimeter frame.

Preferably said at least some of said interstices are at least in part bounded by an at least in part surrounding flange running between bounding said structural webs.

Preferably said structural support is at least predominantly of aluminium.

Preferably said structural support providing member is aluminium.

Preferably said structural support providing member is cast as a unitary item.

Preferably said structural support providing member is die cast. Preferably said plate is aluminium.

Preferably said top plate is an aluminium alloy.

Preferably said plate is affixed to said structural support providing member.

Preferably said plate is welded to said structural support providing member.

Preferably said plate includes a major side facing said structural support providing member, and on said major side there are means to locate with at least some of said structural webs.

Preferably said means to locate are lugs or flanges upstanding from the major surface of said top plate and abut either side of said structural webs of said structural support providing member. Preferably said top plate is engaged to said structural support by any one or more of: a) Welding, b) Threaded or similar fastening, c) Adhesives, or d) any combination thereof.

Preferably said plate is a tread plate and said cover is for use to engage with an in-ground access opening.

Preferably said top plate includes, on its upper presenting major surface, a tread or grip enhancing pattern. Preferably said in-ground access opening is a manhole.

Preferably said access cover has locking means to releasably engage with a surrounding or perimeter frame of in-ground access opening.

Preferably said structural support providing member includes a frame web extending generally in a direction lateral to the planar direction of said structural support providing member.

Preferably said frame portion is continuous about the periphery of said lattice of structural webs.

Preferably said structural webs include a first plurality of structural webs extending in a first direction and a second plurality of structural webs extending in a second direction, perpendicular to said first plurality , both said first and second pluralities extending between inner edges of said frame portion.

Preferably said structural support is circular in shape having radial webs.

Preferably said first direction extending structural webs extend lateral to the second direction extending structural webs. Preferably said surrounding flange is disposed more to the lower side of said structural webs.

Preferably the interstices are located between at least two adjacent first direction extending structural webs are at least in part bounded by a said closure flange. Preferably such interstices are ones not bounded by said framed perimeter.

Preferably such interstices are ones centrally extending across said structural support providing member.

Preferably the interstices between at least two second direction extending structural webs are at least in part bounded by a closure flange. Preferably such interstices are ones not bounded by said framed perimeter.

Preferably such interstices are ones centrally extending across said structural support providing member.

Preferably all said interstices are bounded by said closure flange.

Preferably said access cover in plan form is square, rectangular, or of other multisided polygonal shape, including triangular and circular.

Preferably said structural support is circular in shape having radial webs.

In another aspect the present invention consists in a method of forming a load bearing access cover, assembly or components thereof, said load bearing access cover to at least in part close an opening, comprising or including the steps of, a) providing, a unitary cast structural support providing member

(hereinafter "structural support") defining an upper side and a lower side including, i) a lattice of structural webs defining a plurality of interstices, wherein at least some interstices are open to both said upper and lower sides, and ii) a frame portion at least in part surrounding a periphery of said lattice, said frame portion connecting between at least some of said structural webs, and b) engaging a top plate to said structural support providing member from above, said top plate being at least substantially coextensive with said structural support, to form a unitary load bearing structure. Preferably said top plate is engaged to said structural support by any one or more of: a) Welding b) Threaded or similar fastening, c) Adhesives, or d) any combination thereof.

Preferably said top plate is engaged to said structural surround by welding. Preferably said top plate locates to the upper side of and parallel to a planar profile of said structural support.

Preferably said at least some of said interstices are at least in part bounded by an at least in part surrounding flange running between bounding said structural webs.

Preferably at least said structural support is at least predominandy of aluminium.

Preferably said structural support providing member is cast as a unitary item. Preferably said top plate is aluminium.

Preferably said top plate includes a major side facing said structural support providing member, and on said major side there are means to locate with at least some of said structural webs.

Preferably said means to locate are lugs or flanges upstanding from the major surface of said top plate and abut either side of said structural webs of said structural support providing member.

Preferably said top plate includes, on its upper presenting major surface, a tread or grip enhancing pattern.

Preferably said method includes the step of locating locking means at least in part in said access cover releasably engage with a surrounding or perimeter frame of an in-ground access opening.

Preferably said access cover in plan form is square^rectangular, or of other multisided polygonal shape, including triangular and circular.

In yet a further aspect the present invention consists in an in situ opening cover located in or on the ground and engaged with a complementary perimeter frame, said opening cover comprising or including, a) a lattice of structural webs defining a plurality of interstices, wherein at last some interstices are open to both said upper and lower sides, and b) a frame portion at least in part surrounding a periphery of said lattice, said frame portion connecting between at least some of said structural webs, and a top plate engaged to the upper side of said structural support providing member, said plate being of a perimeter commensurate with a perimeter of said structural support, wherein said structural support and said top plate are engaged or able to be engaged to form a unitary load bearing structure.

Preferably said perimeter frame may be permanently located with and about ground level opening.

Preferably said perimeter frame is made of aluminium.

In a another aspect, the present invention consists of a method of making an access cover as defined above without the use of sand casting.

In a further aspect, the present invention consists of a load bearing access cover as herein described with reference to any one or more of the accompany drawings.

Preferably said access cover is made by die casting. This invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, and any or all combinations of any two or more of said parts, elements or features, and where specific integers are mentioned herein which have known equivalents in the art to which this invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth.

A preferred form of the present invention will now be described with ' reference to the accompanying drawings.

Figure 1 is a perspective top view of a plate forming part of the top cover of the present invention, Figure 2 is a perspective top view of the structural support for the top cover,

Figure 3 is a perspective bottom view of the access cover frame that the access cover can fit,

Figure 4 is a perspective top view of Figure 3,

Figure 5 is a perspective bottom view of the structural support of Figure 2, Figure 6 is a perspective bottom view of the top cover of Figure 1,

Figure 7 is a plan view of a further embodiment cover of the present invention,

Figure 8 is a plan view of a further embodiment cover of the present invention, Figure 9 is a sectional view through section AA of Figure 7 showing a cover engaged with a frame engaged to the ground to provide closure to an access opening in the ground,

Figure 10 is a plan view of yet a further embodiment of an access cover according to the present invention, Figure 11 is a perspective view of an access cover fully assembled,

Figure 12 is perspective view of the bottom of the access cover fully assembled as shown in Figure 11, and

Figure 13 shows in bottom perspective view a further embodiment wherein complementary structural webs extend from the top plate also to engage with structural webs on the structural support , and

Figure 14 shows a similar view to Figure 13 in section view along cutting plane AA.

Figure 1 illustrates a top plate 1 to form part of the access cover of the present invention. The top plate 1 is preferably of a thickness which is relatively thin and of a perimeter shape which is substantially commensurate with the plan view of the final assembled access cover assembly. The top plate 1 is for example of a quadrilateral shape but may alternatively be of anyi-number of sides: Shown also is a circular shape where it is to be used in a manner to provide a circular closure to an opening in the ground. The top plate 1 is preferably made from an aluminium material such as an aluminium alloy but may alternatively be made from a steel material such as a cast iron steel or rolled steel. However to take advantage of reduced weight of the overall assembly of the access cover of the present invention, aluminium is preferred.

The top plate 1 is to engage with a structural support 2. The structural support 2 is made from aluminium such as a castable aluminium alloy. In this embodiment the join between the top plate 1 and the structural support 2 is toward the upper surface of the assembly of the two.

In another embodiment of the present invention the top plate 1 may have structural webs 5' and 6' extending from its underside complimentary to those 5 and 6 extending up from die structural support 2. In this embodiment the join line is no longer at the upper surface of the assembly but may be towards the middle of the resultant assembly of the top plate 1 and structural support 2. The attachment of the two may still be by methods as herein described.

In the most preferred form the structural support 2 is die cast in a mould. The particular construction of the structural support 2 is such that it can be released from the die cast mould by a two part separation of the mould in which the

structural support 2 is cast. As such the configuration of the structural support includes no undercut or recessed features which, as will be appreciated by a person skilled in moulding technology would result in much more complex moulding equipment needing to be utilised. The structural support 2 of die present invention is able to be released from a two part separation of a die cast mould. In the example shown in Figure 2 and 5, the structural support 2 includes a frame portion 3 which preferably extends continuously to define a framed perimeter of the structural support 2. The frame portion 3 is preferably a flange which extends in a direction parallel to the load direction to be received on top of the access cover or top plate 1. As such the frame portion 3 extends substantially in a direction parallel to the normal of the top plate 1.

In an alternative configuration where the access cover is circular as for example shown in Figure 8, the frame portion 3 is substantially circular in shape to define the frame to the structural support 2 of such a circular cover. Whilst the frame portion 3 is preferably continuous it need not be of a constant cross sectional shape or be continuous to define a fully framed perimeter of the structural support 2. In some instances also it may have a tapered dross section that has reduced thickness from top to bottom Extending inwardly from the frame portion 3 is a plurality of structural webs

5, 6. These webs extend preferable between opposed ends of the frame portion 3. As such they extend substantially across the entire width and length of the cover. In the quadrilateral form of the cover, the lateral and longitudinal webs 5, 6 preferably extend at 90 degrees to each other to create a lattice like structure. In the configuration as shown in Figures 2 and 5, there are two longitudinal webs and 6 transverse webs.

The number of webs will vary depending on the required load rating of the access cover.

Intermediate of the webs 5, 6 and also the frame portions 3, a plurality of interstices 7 is defined. Each of the interstices 7 may be have an opening from top side to bottom side of the structural support 2. However at least a selection of the

interstices 7 are partially enclosed by a closure flange 8. In the most preferred form there is an array of interstices 7 which extend between opposed edges of the frame portion 3 which are at least in part bounded by a closure flange 8.

It can be seen that the array A of the structural support 2 defined between the two longitudinal webs 6 are partially enclosed by the closure flanges 8. Likewise three arrays B, C, D extending between adjacent lateral webs 5 include such closure flanges 8 extending from side to side of the frame portion 3.

Structurally it will be appreciated that the provision of such closure flanges 8 extending substantially across all or at least most of both the width and the length of the structural support will enhance the structural rigidity of the structural support 2 as far as the bending moment of the structural support 2 is concerned. Even with the inclusion of the closure flanges 8, there is still no undercutting occurring to the structural support. As such a two part mould release can still be conveniently achieved for a structural support 2 as shown in Figures 2 and 5. The webs 5, 6 preferably extend also in a direction substantially normal to the plate 1 and the closure flanges 8 extend substantially parallel to or possibly at a slight angle to the plane of the plate 1.

With reference to Figure 5, it can be seen that the lower most edges of the webs 5, 6 toward the frame portion 3 provide a nonlinear edge along which the closure flanges 8 extend. Therefore as such the closure flanges 8 do not strictly lie in a plane parallel with the plane of the plate 1.

Furthermore it can also be seen with reference to Figure 5 that the closure flanges do not provide a complete closure to the interstices. It can be seen that the closure flanges still include an opening 12 but there is sufficient size in the closure flanges to be able to enhance the bending moment of the structural support.

In order to create the sandwich like construction, the top plate 1, subsequent to the forming of the unitary cast structural support 2, engaged to the upper side of the structural support 2. The engaging surface 10, in this case the lower surface of the top plate 1 may include locating features 13 where it mates to the top plate 1 which can engage with the upper edges of the webs 5, 6.

In the preferred embodiment the locating features 13 are channels to accept the upper edges of the webs 5 and 6.

The top plate 1 can then be attached to the structural support 2 or otherwise fastened thereto to create a cover assembly 14. The attaching of the top plate 1 to the structural support 2 can be by welding, fasteners (whether threaded or otherwise, eg rivets), adhesives or any combination of these. In the preferred embodiment the top plate 1 is welded to the structural support 2.

The openings 12 of the closure flanges 8 still allow for access to be obtained to the mating surface of the top plate 1 and the webs 5, 6 for the purposes of such welding

With reference to Figure 12, an alternative configuration of the structural support 2 engaged with the top plate l.is shown.

The resulting two part access cover 14 rendered as a one part buy attachment

(eg by welding fastening or otherwise) of a top plate 1 to a structural support 2 can engage within a perimeter frame 15 as shown in Figure 9. The perimeter frame can be permanently or semi-permanently affixed to or in the ground or material located in the ground, e.g. a concrete surround frame or capping.

The resulting cover in aluminium measuring 1200mm x 600mm weighs 38 kg and has a rating of 210 kN. The same cover in steel with the same load rating weights 90 kg. The weight saving of the present invention can therefore be seen. Locks 11 or apertures for locks may be present to fasten the access cover 14 to the perimeter frame 15 may be provided. The perimeter frame 15 allows for the cover 14 to engage therewith and preferably sit flush with the upper surface 16 of the surrounding ground, road or footpath, or capping with which the cover is to provide a closure to the utility chamber 17 or similar below, access opening 17.